Kiln for annealing glass.



No. 805,069. PATENTED NOV. 21,1905.

H. K. HITGHGOGK. KILN FOR ANNEALING GLASS.

APPLICATION FILED JULY 17 1905.

3 SHEETS-SHEET 1.

WITNESSES: F INVENTOR PATENTED NOV. 21, 1905.

H. K. HITCHGOCK.

KILN FOR ANNEALING GLASS.

APPLICATION FILED JULY 17. 1905.

3 SHEETS-SHBBT 3.

u a n ll 1 L \N v, I /t I I l'l'z/ 4 II s v s I s I 5 UNITED STATES PATENT OFFICE.

KILN FOR-ANNEALING GLASS.

Specification of Letters Patent. 7

Patented NOV. 21, 1905.

Application filed July 17, 1905. Serial No. 270,086.

To all whom it may concern:

Be'it known that I, HALBERT K. HITCHCOCK, a citizen of the United States, residing at Tarentum, in the county of Allegheny and State of Pennsylvania, have invented or discovered certain new and useful Improvements in Kilns for Annealing Glass, of which improvements the following is a specification.

The invention described herein relates to certain improvements inkilns for annealing glass, and has for its object a construction and com bin-ation of parts of a kiln whereby the dissipation of heat will progress equally, or substantially so, from all portions of the surfaces of the glass. The lowering of the temperature of a kiln and its contents is due to heat radiated from the outer surfaces of the kiln, and the heat thus lost is proportional, or approximately so, to the heat absorbed by the inner surfaces of the kiln. The heat absorbed from any given portion of the glass is approximately proportional to the area of the kiln-wall opposed to such portionas, for example, the vertical walls and portions of the crown and hearth adjacent thereto form the heat-absorbing area opposed to the edges of the sheet, while the heat-absorbing area for a given portion of the sheet near its middle will be formed by a portion of the crown or hearth of approximately the same area as the given portion of the sheet. Hence the edges of the sheet should lose its heat much more rapidly than portions in the middle of the sheet, and this has been found to be the case, so that sheets annealed in kilns as at present constructed and operated are subjected to strains which cause the sheet to bend or buckle or produce vents along the edges of the sheet. In order to avoid the formation of these strains along the edges of the sheets, the areas of the walls opposed to the edge are reduced as far as possible by lowering the edges of the crown into close proximity to the hearth.

In order to prevent strains which would result from introducinga hot sheet into a cooler oven, I make provision for heating (while empty) all parts of the oven to or slightly above the temperature of the sheet to be charged into the oven and prevent any loss of heat except that due to radiation from the outer surfaces of the oven.

As the under surface of sheet as it comes from the casting-table is colder than the upper surface, it is desirable to equalize the temradiate freely from its under surface. hearth of the first oven is preferably made perature throughout the sheet while the latter retains some degree of plasticity and while all strains can be relieved by the natural ductility of the glass. Hence the hearth of the first of the series of ovens is made somewhat thicker than the crown, so that radiation will be more rapid from the upper surface and the tern-- peratures of the two surfaceswill equalize. The succeeding ovens are preferably constructed so that the radiation from all parts will be the same.

The invention is hereinafter more fullydescribed and claimed.

In the accompanying drawings, forming a part of this specification, Figure 1 is a top plan View of my improved ovens. Figs. 2 and 3 are sectional elevations on planes indicated, respectively, by the lines II II and III III, Fig. 1. the gas-regulating valve. Figs. 5 and 6 are detail views of the stowing-tool.

In the practice of my invention the side walls 1, which support the hearth 2 and crown 3, are immediately below the skewback and are curved to overhang, as at t, the edges of the sheet A. The side walls between the hearth and skewbacks are made as low as possible, thus reducing the radiation area opposed to the edges of the sheet. The crown or roof is made in four sections springing from the four side walls and joining each other in the manner of a hip roof, so that the surfaces opposed to the several edges of the sheet are symmetrical. It will be observed that the hearths and crowns of all the ovens except the first of the series are made of approximately the same thickness and the hearth is so supported that heat may The somewhat thicker than the crown, so that the temperatures of the upper and under surfaces of the sheet may be equalized, as heretofore stated. It is preferred that the walls of the oven should have a thickness proportional to their heat-dissipating capacity per square foot of their interior surfaces. The sill 5 under the stowing-slot 6 is made vertically movable, so that it may serve to close said slot after the charging of a sheet. In the construction shown the brick or tile forming the sill are Fig. 4 is a sectional detail view of supported on a plate 7. This sill is adapted to be raised and lowered by any suitable means, as the hydraulic jack, consisting of the cylinders 8 and pistons 9.

A series of holes 11 are formed through the hearth along the side walls of the ovens, and into these holes project burners 12, connected to suitable gas-supply pipes 13. The main flow of gas to the burners is controlled by a suitable valve mechanism; but a constant flow of gas to the burners suflicient to insure the ignition of the gas when a full flow is turned on is maintained through a by-pass 14 around the main valve. In operating the ovens it is proposed to equally heat all parts of each oven after a sheet has been removed and before a new sheet is charged to a temperature equal to or a little above that of the sheet to be charged. The operation of the main valve for this purpose can be effected by hand; but

it is preferred to make the closing of the valve automatic after a predetermined interval, so that the reheating may be always the same, or approximately so. A desirable construction for this purpose is shown in Fig. 4E and consists of avalve 15, adapted to be opened by a spring 16, having a tension less than that of the closing-spring 17, operating on the valve through a lever 18 and the stem of valve 15. One end of the lever is connected to a collar 19 on the rod 20 of the piston 21. When the outer end of the lever is raised to open or permit of the opening of the valve 15, the piston will be drawn down and the spring 17 placed under tension. The movement of the piston will force fluid contained in the cylinder 22 from one end through the passage 23 past the check-valve 24 to the opposite end thereoi. The return flow of the fluid under the action of spring 17 is through the passage 25 and is controlled by the adjustable valve 26. The length of time the valve 15 shall remain open can be regulated by the adjustment of the valve 26, while the volume of gas flowing is controlled by the cock.

Provision is made for the escape of products of combustion by a perforated cup 27, inserted in the crown of the furnace, the openings in which allow of the free escape of the gases of combustion, but prevents any radiation of heat into the damper at the top and which also serves to keep in the hot gas until the oven is completely filled. The escape of heat and the entrance of cold air is prevented by a valve 28, which should be opened and closed simultaneous with the movements of the valve 15. To accomplish this, the cap or valve 28 is connected by a rod 29 to an arm movable by a diaphragm peripherally secured to a shell 30. This shell is connected to the gas-pipe 13, so that when the valve 15 is opened the diaphragm is shifted and the valve 28 opened, allowing the escape of products of combustion. When the diaphragm is relieved of pressure by the closing of the valve 15, the valve 28 will close. It will be understood that the operator will shift the valve 15 as soon as a sheet has been shifted from the oven, and the valve 26 having been properly adjusted the valve 15 will be closed as soon as the oven has been properly reheated.

It is characteristic of my improvement that provision is made for heating the ovens to or slightly above the temperature of the sheet to be charged, and in operating the ovens after they have been properly heated and the gas turned off opportunity is afforded for an equalization of temperature in all parts of the oven before the sheet is charged in. Hence there cannot be any sudden reduction or increase of temperature in any part of the sheet and there will be a gradual and even cooling of all'parts.

As is well known to those skilled in the art, an oven having a flat top or one arching only in one direction is exceedingly diflicult to maintain at the same temperature in all parts.

If, however, the crown be made to arch in allv directions, as described, there will be such a radiation and reflection of heat from one part to another that all parts will have practically the same temperature.

I claim herein as my invention 1. An oven for annealing glass having its walls so constructed and proportioned as to have the same heat-dissipating capacity at all points.

2. An oven for annealing glass having its hearth and crown constructed to form free radiating-surfaces and of equal or approximatelyjequal thickness whereby the heat-dissipation from all points of the hearth and crown may be approximately equal.

3. An oven for annealing glass having vertical passages along all its side Walls, in combination with burners connected to a gas-supply and arranged to discharge into said passages to heat said side walls to a temperature approximately that of the glass to be annealed.

1. An oven for annealing glass having vertical passages along all its side walls in combination with burners connected to a gas-supply and arranged to discharge into said passages, and a valved outlet for the-escape of products of combustion.

5. An oven for annealing glass having passages for the admission of gas, in combination with burners connected to a gas-supply and arranged to discharge into said passages, a valve controlling the flow of gas and automatic means for closing said valve.

6. An oven for annealing glass having passages for the admission of gas, burners coning glass, the method herein described Which consists in moving a sheet through a series of ovens and heating each oven to a temperature equal to'or slightly higher than the discharging temperature of the'preceding oven before shifting the sheet from the latter.

In testimony whereof I have hereunto set my hand.

HALBERT K. HITCHCOCK. Witnesses:

FRANCIS VERNAN, CHARLES BARNETT. 

